Activity Instructions:

Introduction: Liquid Crystal (LC) is a Phase of Matter (5-10 min)
Have students brainstorm the different properties of liquids, solids (crystals),
and gases. Note that liquid crystal (LC) is a special phase of matter and have
students brainstorm its properties (e.g., liquid-solid hybrid) based on the
discussion of liquids and solids.

Optional: Have students arrange the phases of matter based on randomness at
the atomic level. Note that atoms in a liquid crystal phase are less random
than atoms in a liquid phase and more random than atoms in a solid phase.

Bubble
Activity: LCs Reflect Different Colors of Light (10 min)
Have students blow bubbles, a particular type (i.e. lyotropic) of LC, and make
observations about how their colors change from when they were brand new to
right before they pop. (Bubbles will be less colorful as they dry out and get
closer to popping.) Note that bubbles reflect all the full spectrum of colors
in a rainbow.

Introduce Temperature Sensitive LCs (10 min)

Note that there are many different types of LC  including LCs that respond
to temperature changes. Have students rub glass vials containing temperature
sensitive LCs and make observations, noting that heat is transferred to the
LCs from the students hands. Ask students why these LCs might change color
at different temperatures.

CAUTION: Do not allow students to open the vials. This type of liquid
crystal is toxic.

Experiment: Compare Different LCs at Different Temperatures (15 min)

Give the students liquid crystal thermal sheets that change color in response
to different temperature ranges. Have them use their hands with or without hand
warmers to order the thermal sheets from low temperature sensitive to high temperature
sensitive.

LC Sensor Activity: LC Sensors Can "See" What Our Eyes Can't
(15 min)

Use LC sensors to see the invisible thermal print that your hand leaves when
removed from a tabletop. Place a hand warmer over an envelope containing a magnetic
shape/message. Remove the hand warmer and wait a few seconds before placing
on a high temperature sensitive liquid crystal sheet. Note the appearance of
the message on the LC sheet.

Have the students use their thermal sheets to decode other magnetic shapes/messages
hidden inside envelopes. They may find the hand warmer and ice pack useful.

Brainstorm Potential Uses for LCs and LC Sensors (optional)
Have students come up with their own ideas for how LC products and sensors might
be used in the real world.

Required Background Information:

Phases of Matter
The atoms of solid are compact with their positions and orientations fixed,
whereas those of a liquid can move around, assuming the shape of whatever container
the liquid is in. Liquid crystals also have the fluidity of a liquid but their
movement is coordinated along the same direction. Therefore, one atom in the
liquid crystal phase has an impact on the orientation of another atom close
by. Liquid crystals are made by boiling certain kinds of organic compounds and
then, subsequently cooling them. For a more in-depth look at the structure of
liquid crystals, see the Background
for the Teacher transparencies.

Nano
Nano is a prefix that means one-billionth of something. For example, nanometer
is one-billionth of one meter. The nanoscale is useful in describing the size
of atoms, which are subunits of matter. Nanotechnology refers to the design
of technology and tools at the nanoscale to manipulate and/or visualize atoms.
Phases of matter differ in how much freedom the atoms have in moving around.
For example, when atoms have very little freedom, the overall structure is rigid
as in a solid.

Light
Light is wave. Different colors of light are characterized by a different wavelength,
which is on the order of 400 to 700 hundred nanometers in the visible spectrum.
White light consists of all the colors of the rainbow. When white light hits
the atoms of a liquid crystal, the orientation of these atoms may allow only
certain wavelengths or colors of light to be reflected back to our eyes.

The Nanotechnology Activity Guides are a product of the Materials Research
Science and Engineering Center and the Internships in Public Science Education
Project of the University of Wisconsin - Madison. Funding provided by the National
Science Foundation.